Exposure to anticancer drugs can result in transgenerational genomic instability in mice

Abstract

The genetic effects of human exposure to anticancer drugs remain poorly understood. To establish whether exposure to anticancer drugs can result not only in mutation induction in the germ line of treated animals, but also in altered mutation rates in their offspring, we evaluated mutation rates in the offspring of male mice treated with three commonly used chemotherapeutic agents: cyclophosphamide, mitomycin C, and procarbazine. The doses of paternal exposure were approximately equivalent to those used clinically. Using single-molecule PCR, the frequency of mutation at the mouse expanded simple tandem repeat locus Ms6-hm was established in DNA samples extracted from sperm and bone marrow of the offspring of treated males. After paternal exposure to any one of these three drugs, expanded simple tandem repeat mutation frequencies were significantly elevated in the germ line (sperm) and bone marrow of their offspring. This observed transgenerational instability was attributed to elevated mutation rates at the alleles derived from both the exposed fathers and from the nonexposed mothers, thus implying a genome-wide destabilization. Our results suggest that paternal exposure to a wide variety of mutagens can result in transgenerational instability manifesting in their offspring. Our data also raise important issues concerning delayed transgenerational effects in the children of survivors of anticancer therapy.epigenetic | genetic risk

Evidence relevant to untargeted and transgenerational effects in the offspring of irradiated parents

“…Results consistent with the above were obtained also in further X-ray investigations by Barber et al [ 49] and Abouzeid Ali et al [ 22], as well as generally similar results being obtained for other DNA-damaging agents (namely, ENU [48] and three chemotherapeutic drugs [24]). Following 1 Gy of X-rays in utero at 12 days of gestation and mating at 8 weeks of age, raised ESTR mutation frequencies were observed in the germline and somatic cells of the first-generation (F 1 ) offspring after paternal (F 0 ) in utero irradiation, but not after maternal in utero irradiation [49].…”

“…From the very high frequencies of induction it was concluded that mutations arise from some form of radiation-induced instability leading to non-targeted events in the irradiated germline. More recent studies, entirely from the Dubrova group, using pedigree analysis and/or SM-PCR analysis of the F 0 sperm, have confirmed and extended these results to a variety of additional biological and exposure conditions (including ENU exposure [48], in utero irradiation [49],, chemotherapeutic drug exposures [24, 50] and lower- dose and chronic irradiation [23]), and to ESTR mutations in somatic cells of the irradiated (F 0 ) mice [49]. Results from all of the above showed high-frequency induction of ESTR mutations in the directly-irradiated germline or somatic tissues.…”

“…In particular, a number of studies of expanded simple tandem repeat (ESTR) mutations in F 1 offspring of irradiated male mice suggested excess frequencies that appeared to increase with increasing dose over the range of a few Gy, in partial contrast to some human studies with less apparent dose dependence, albeit from rather sparse data [13]. Very recent studies of male mice have presented further evidence that transgenerational effects may result from ionising radiation exposure [22, 23] as well as from commonly used chemotherapeutic agents [24]. Should such effects translate to humans they would be of potential concern to men who have undergone radiotherapy and wish to have children.…”

Non-targeted effects of ionising radiation—Implications for low dose risk

“…It has therefore been hypothesised that radiation-induced complex double-strand DNA breaks may represent such triggering events [96]. To establish whether GI is attributed to the induction of a specific subset of DNA lesions, studies by Dubrova et al have analysed the transgenerational effects of paternal treatment by a number of mutagens, exposure to which mostly causes alkylation of DNA and other types of DNA damage [97, 98]. The results of these studies clearly show that paternal exposure to the alkylating agent ethylnitrosourea, as well as to three anticancer drugs cyclophosphamide, mitomycin C and procarbazine can destabilise the offspring’s genome in a similar manner to that following paternal irradiation.…”

Cigarette smoking significantly alters sperm DNA methylation patterns

“…Barber et al, 2002; R. C. Barber et al, 2006; Dubrova, 2003; Dubrova et al, 2008; Glen et al, 2012). Thus, these data suggest that smoke exposure might induce lasting genetic and epigenetic changes that could impact subsequent unexposed generations.…”